The M79 Grenade Launcher

The M79 was a single shot weapon that looked like a sawed off
shotgun. It could shoot an explosive round 350 meters in a gentle
arc. Its muzzle speed was slow enough to watch the egg shaped
grenade on its way to the target. It kicked like a mule and was
rarely fired from the shoulder as intended. Instead it was fired
from the hip using the "Kentucky windage" method of
aiming.